Here is an idea:
1) Make sure you have your request for evidence of a registered by-law, minutes of a meeting and a proper notice of that meeting in writing.
2) Get together with the parents or carers of other children and organise to supervise your children using the pool responsibly on a regular schedule. Make sure you are compliant with the model by-law quoted by JT, even if it does not apply to your site. It shows what the legislators regarded as reasonable.
3) See what happens. Perhaps nothing.
4) If you are issued with a notice to comply with the by-law, reiterate your request, in writing, for evidence that the by-law exists and is valid.
5) If no evidence is forthcoming, continue the above cycle.
6) If it turns out the by-law was adopted by a properly constituted meeting and registered, investigate further whether it can be thrown out by the Tribunal as harsh and unreasonable and substituted with the model by-law, which the Tribunal should accept as reasonable, or attempt to get the same outcome by putting a motion to a general meeting.